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Bundoora, Australia

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Bundoora, Australia
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Li Y.,Wuhan University of Technology | Li Y.,University of South Australia | Qian G.,University of South Australia | Brown P.L.,Research Avenue | Gerson A.R.,Blue Minerals Consultancy
Geochimica et Cosmochimica Acta | Year: 2017

Dissolution and oxidation of sulfide minerals play key roles in both acid and metalliferous rock drainage and supergene enrichment. Surface speciation heterogeneity, critical to understanding mechanisms of mineral sulfide dissolution, has to date largely not been considered. To this end synchrotron scanning photoelectron microscopy (SPEM) was employed to examine freshly fractured and partially dissolved chalcopyrite (CuFeS2) surfaces (pH 1.0 HClO4 solution, redox potential 650 mV relative to a standard hydrogen electrode, 75 °C). S2− (bulk), S2 2− and Sn 2− were found to be present on all samples at varying concentrations. Oxidation was observed to take place heterogeneously at the sub-micron scale. As compared to chalcopyrite partially dissolved for 5 days, extended dissolution to 10 days did not show appreciably enhanced oxidation of surface species; however surface roughness increased markedly due to the growth/overlap of oxidised sulfur species. On addition of 4 mM iron both S0 and SO4 2− were observed but not SO3 2−, indicating that the greater Fe3+ activity/concentration promotes heterogeneous sulfur oxidation. On contact of pyrite (FeS2) with chalcopyrite, significantly greater chalcopyrite surface oxidation was observed than for the other systems examined, with S0, SO3 2− and SO4 2− being identified heterogeneously across the surface. It is proposed that chalcopyrite oxidative dissolution is enhanced by increasing its cathodic area, e.g. contacting with pyrite, while increased Fe3+ activity/concentration also contributes to increased dissolution rates. The high degree of surface heterogeneity of these surface products indicates that these surfaces are not passivated by their formation. These results suggest that chalcopyrite dissolution will be accelerated when in contact with pyrite at solution redox potential intermediate between the rest potentials of chalcopyrite and pyrite (560 mV and 660 mV, respectively) and/or iron rich acidic waters with resulting enhanced formation of secondary sulfur containing species and release of copper and iron. This in turn suggests accelerated supergene formation and enhanced metalliferous drainage under these conditions. © 2017 Elsevier Ltd


Powell K.J.,University of Canterbury | Brown P.L.,Research Avenue | Byrne R.H.,University of South Florida | Gajda T.,University of Szeged | And 4 more authors.
Pure and Applied Chemistry | Year: 2013

The numerical modeling of ZnII speciation amongst the environmental inorganic ligands Cl-, OH-, CO32-, SO42-, and PO43-requires reliable values for the relevant stability (formation) constants. This paper compiles and provides a critical review of these constants and related thermodynamic data. It recommends values of log10βp,q,r° valid at Im = 0 mol·kg-1 and 25 °C (298.15 K), and reports the empirical reaction ion interaction coefficients, Δ∈required to calculate log10βp,q,r values at higher ionic strengths using the Brønsted-Guggenheim-Scatchard specific ion interaction theory (SIT). Values for the corresponding reaction enthalpies, ΔrH, are reported where available. There is scope for additional high-quality measurements for the Zn2+ + H+ + CO32-system and for the Zn2+ + OH-and Zn2+ + SO42-systems at I > 0. In acidic and weakly alkaline fresh water systems (pH <8), in the absence of organic ligands (e.g., humic substances), ZnII speciation is dominated by Zn2+(aq). In this respect, ZnII contrasts with CuII and PbII (the subjects of earlier reviews in this series) for which carbonato-and hydroxido-complex formation become important at pH > 7. The speciation of ZnII is dominated by ZnCO3(aq) only at pH > 8.4. In seawater systems, the speciation at pH = 8.2 is dominated by Zn2+(aq) with ZnCl+, Zn(Cl)2(aq), ZnCO3(aq), and ZnSO4(aq) as minor species. This behaviour contrasts with that for CuII and PbII for which at the pH of seawater in equilibrium with the atmosphere at 25 °C (log10 {[H+]/c°} ≈ 8.2) the MCO3(aq) complex dominates over the MCln(2-n)+ species. The lower stability of the different complexes of ZnII compared with those of CuII, PbII, and CdII is also illustrated by the percentage of uncomplexed M2+ in seawater, which is ca. 55, 3, 2, and 3.3% of [MII]T, respectively. © 2013 IUPAC.


Trenfield M.A.,Environmental Research Institute of the Supervising Scientist | Trenfield M.A.,University of Queensland | McDonald S.,Curtin University Australia | Kovacs K.,University of Szeged | And 7 more authors.
Environmental Science and Technology | Year: 2011

Fulvic acid (FA) from a tropical Australian billabong (lagoon) was isolated with XAD-8 resin and characterized using size exclusion chromatography, solid state cross-polarization magic angle spinning, 13C nuclear magnetic resonance spectroscopy, elemental analysis, and potentiometric acid-base titration. Physicochemical characteristics of the billabong FA were comparable with those of the Suwannee River Fulvic Acid (SRFA) standard. The greater negative charge density of the billabong FA suggested it contained protons that were more weakly bound than those of SRFA, with the potential for billabong water to complex less metal contaminants, such as uranium (U). This may subsequently influence the toxicity of metal contaminants to resident freshwater organisms. The complexation of U with dissolved organic carbon (DOC) (10 mg L-1) in billabong water was calculated using the HARPHRQ geochemical speciation model and also measured using flow field-flow fractionation combined with inductively coupled plasma mass-spectroscopy. Agreement between both methods was very good (within 4% as U-DOC). The results suggest that in billabong water at pH 6.0, containing an average DOC of 10 mg L-1 and a U concentration of 90 μg L-1, around 10% of U is complexed with DOC. © 2011 American Chemical Society.


Powell K.J.,University of Canterbury | Brown P.L.,Research Avenue | Byrne R.H.,University of South Florida | Gajda T.,University of Szeged | And 4 more authors.
Pure and Applied Chemistry | Year: 2011

The numerical modeling of CdII speciation amongst the environmental inorganic ligands Cl-, OH-, CO3 2-, SO4 2-, and PO4 3- requires reliable values for the relevant stability (formation) constants. This paper compiles and provides a critical review of these constants and related thermodynamic data. It recommends values of log10 βp,q,r° valid at Im = 0 mol kg-1 and 25 °C (298.15 K), along with the equations and empirical reaction ion interaction coefficients, Δε, required to calculate log10 βp,q,r values at higher ionic strengths using the Brønsted-Guggenheim-Scatchard specific ion interaction theory (SIT). Values for the corresponding reaction enthalpies, ΔrH, are reported where available. Unfortunately, with the exception of the CdII-chlorido system and (at low ionic strengths) the CdII-sulfato system, the equilibrium reactions for the title systems are relatively poorly characterized. © 2011 IUPAC.


Costine A.,CSIRO | Nikoloski A.N.,Murdoch University | Costa M.D.,CSIRO | Chong K.F.,Murdoch University | And 2 more authors.
Minerals Engineering | Year: 2013

Brannerite is a refractory uranium mineral from which it is very difficult to liberate the uranium. Hence in commercial mineral processing operations, brannerite often reports to the residue. This paper will show that for a pure form of natural brannerite nearly complete extraction of uranium (∼99%) is achievable under practical conditions. The efficient extraction of uranium from ores containing brannerite requires a detailed understanding of the fundamental mechanisms governing the rate and extent of dissolution. These mechanisms are often complicated by the presence of gangue minerals which consume reagents and impact on the solution chemistry. In this study, the acidic ferric sulphate leaching of an exceptionally pure, natural brannerite mineral (35.8% U, 20.1% Ti) was investigated under atmospheric conditions. Hence the variation in mineral composition was not present as a complicating factor and the results were able to identify some of the inhibiting mechanisms, and also the preferred conditions for the leaching of brannerite in an acidic ferric sulphate system. The effects of temperature (40-80 C), ferric ion concentration (0-100 g/L), H2SO4 concentration (10-200 g/L), redox potential (424-752 mV vs. Ag/AgCl), and particle size on uranium and titanium extractions were studied for leach times up to 48 h. Under relatively mild conditions (40 C, 24 h leach time, 40 g/L H2SO4), the extent of uranium extraction was 94.4%. The extractions improved with the use of a higher temperature, a finer particle size, and a longer leach time. The presence of ferric iron was essential for enhanced dissolution rates, but had only a minor effect on the final uranium extractions, particularly at 60 C and 80 C. All of the leach residues studied had some crystalline anatase (TiO2) and lead sulphate (anglesite) present. A strong correlation was found between the concentrations of unleached uranium and the amount of titanium precipitated in the residues, which could be explained by the observation of a Ti-enriched diffusion layer on the surface of the dissolving grains of brannerite, which hindered the extraction process. These findings further the current understanding of the extraction process and lead a step closer to elucidation of the mechanism of the extraction process. © 2013 Elsevier B.V. All rights reserved.


Cao G.,Level Inc | Zhang X.,Research Avenue | Zhang H.,Level Inc
TMS Light Metals | Year: 2014

The importance of the cathode assembly thermal-electrical and thermal-mechanical performance cannot be overstated when designing an aluminum reduction cell. However, it is extremely difficult to measure in-service cathode assembly performance or to infer in-service behaviour from any measurements of cathode assemblies at room temperature. A complete thermo-electrical and thermo-mechanical modelling approach has been developed to conduct sequentially coupled simulation of the cathode assembly lifecycle performance. The modelling starts with the cathode rodding process which allows the air gap between the cast iron and carbon to be predicted. The results are built into the subsequent thermo-electrical and thermo-mechanical models of the in cell operation. The cathode voltage drop is then estimated by coupling the predicted contact pressure and temperature with the electrical contact resistance. The model predicted air gaps as well as cathode voltage drop savings due to design changes have been validated by carefully designed experimental measurements for various cathode assembly designs. Copyright © 2014 by The Minerals, Metals & Materials Society.


Bhargava S.K.,RMIT University | Ram R.,RMIT University | Pownceby M.,CSIRO | Grocott S.,Research Avenue | And 3 more authors.
Hydrometallurgy | Year: 2015

Uraninite is mined/processed more than any other uranium mineral for the production of uranium based compounds that are subsequently used to produce nuclear fuel. This review article provides a concise account of the available literature on one of the major processes involved in processing uraninite bearing ores, acid leaching. Improvements in the processes used to leach uraninite are required in order to ensure efficiency in the processing of lower grade uraninite bearing ores with minimal environmental impacts. This in turn requires improvements in our understanding of uraninite leaching. The main topics covered in this review include: uraninite structure, composition and low temperature geochemistry; the chemistry of uraninite leaching; key factors that influence uraninite leaching; and leach process technologies. The research that has been reviewed clearly establishes the influence of parameters such as temperature, acid concentration and particle size. The influence of other parameters however, such as solution Fe3 + to Fe2 + ratio (solution Eh), total Fe concentration, foreign ions present in the leach slurry and uraninite composition is yet to be established. Based on the literature available on the aforementioned factors the chemistry/processes involved in uraninite leaching are quite complex and require significant further studies. From the literature reviewed it is clear that variations in mineral chemistry in individual ore types across multiple deposits also make it essential that before any extraction process is considered, detailed ore characterisation studies of pre- and post-leach residues are of vital importance in order to fully understand the interrelationship between chemistry, mineralogy (ore and gangue), mineral liberation and potential leaching behaviour of uranium. © 2014 Elsevier B.V.


Kaksonen A.H.,CSIRO | Mudunuru B.M.,CSIRO | Hackl R.,CSIRO | Hackl R.,Research Avenue
Hydrometallurgy | Year: 2014

With a projected steady decline of gold ore grade in mineral resources, mining applications enabling efficient metal extraction from low-grade ores are of increasing interest to the minerals industry. Microbial processes may provide one such solution since they can participate in the biogeochemical cycling of gold in many direct and indirect ways. This review examines current literature on the role of microorganisms in gold processing and recovery. The review covers aspects such as the biotechnical pre-treatment of gold ores and concentrates, microbially catalysed permeability enhancement of ore bodies, gold solubilisation through biooxidation and complexation with biogenic lixiviants, and microbially mediated gold recovery and loss from leach liquors. © 2013 Elsevier B.V.


Cheng C.Y.,CSIRO | Boddy G.,Research Avenue | Zhang W.,CSIRO | Godfrey M.,Research Avenue | And 5 more authors.
Hydrometallurgy | Year: 2010

In Part 1 of this paper, two synergistic solvent extraction systems consisting of Versatic 10/LIX63/TBP and Versatic 10/4PC were assessed in batch tests for the separation and purification of nickel and cobalt from synthetic laterite leach solution after iron removal. In Part 2, semi- and fully-continuous tests are reported for the Versatic 10/LIX63/TBP system, with conditions optimised for separating nickel and cobalt from manganese, magnesium and calcium. Semi-continuous extraction tests were conducted using the synergistic organic system consisting of 0.50 M Versatic 10, 0.45 M LIX63 and 1.0 M TBP in Shellsol D70. With a pH profile of 5.5/6.1/6.5 for the three stages EX1/EX2/EX3 at 40 °C, the nickel and cobalt extractions were 99.9% with only 5 mg/L nickel and < 1 mg/L cobalt left in the raffinate. With two stages of scrubbing and a pH profile of 5.4/5.0 at 40 °C, about 2 mg/L manganese and less than 1 mg/L magnesium and calcium were left in the scrubbed organic solution. With two stripping stages and an O/A ratio of 10 at 40 °C using 50 g/L H2SO4 as strip solution, the stripping efficiencies of nickel and cobalt were over 95%. A fully-continuous pilot plant was operated for 280 h. With an O/A ratio of about 2 and a pH profile of 5.5/5.8/6.0/6.3 for the four stages EX1/EX2/EX3/EX4 at 40 °C, both nickel and cobalt were almost completely extracted. The nickel and cobalt concentration in the raffinate was lower than detection limit of 0.2 mg/L. The manganese, magnesium and calcium concentrations in the loaded organic solution were 34, 8 and 1 mg/L, respectively. Using a pH profile of 5.4/5.0 for SC1/SC2 at an O/A ratio of 10 and 40 °C, the manganese scrubbing efficiency was over 96% and the concentrations of manganese and magnesium in the scrubbed organic solution were < 5 mg/L and that of calcium 1 mg/L. Using three strip stages and a strip solution containing 50 g/L H2SO4 and 55 g/L Ni at an O/A ratio of 10 and 40 °C, over 98% Ni and 99% Co were stripped with only 64 mg/L Ni in the stripped organic solution. The nickel concentration in the loaded strip liquor was 86 g/L, giving a ΔNi of 31 g/L. The loaded strip liquor contained less than 1 g/L acid. © 2010 Elsevier B.V.


Cheng C.Y.,CSIRO | Boddy G.,Research Avenue | Zhang W.,CSIRO | Godfrey M.,Research Avenue | And 4 more authors.
Hydrometallurgy | Year: 2010

The separation of nickel and cobalt from impurities such as manganese, magnesium and calcium using solvent extraction with Versatic 10 was largely improved by the addition of a synergistic reagent LIX63 (an α- hydroxyoxime) or 4PC (a pyridine carboxylate ester). With the organic systems containing Versatic 10 alone, the separation factors of nickel and cobalt over manganese were 6 and 15 respectively. When 4PC was added to the system, these increased to 147 and 1870 respectively, and with LIX63, they were even higher at 534 and 7720 respectively. This indicates that the synergistic solvent extraction (SSX) system with Versatic 10 and LIX63 performed very well and better than that with Versatic 10 and 4PC. The SSX system consisting of 0.5 M Versatic 10, 0.45 M LIX63 and 1.0 M TBP in Shellsol D70 performed the best among the systems tested containing LIX63. After a single contact, the extraction of Ni and Co was 99.6% and 96.9%, respectively. Only 6 mg/L Mn, 8 mg/L Mg and 1 mg/L Ca were found in the loaded organic solution. The manganese scrub efficiency was 97.7% at pH 5.3, resulting in a scrubbed organic solution containing only 0.8 mg/L Mn. Over 99% nickel, cobalt and manganese were stripped at pH 2.0, indicating easy stripping of these metals. The SSX system consisting of 0.5 M Versatic 10 and 1.0 M 4PC in Shellsol D70 performed the best among the systems tested containing 4PC. After a single contact, the extraction of Ni and Co was 99.4% and 89.4%, respectively. Some 200 mg/L Mn, 10 mg/L Mg and 48 mg/L Ca were found in the loaded organic solution. The manganese could not be scrubbed at the tested pH range of 5.4-6.0. Very fast Ni and fast Co stripping kinetics were observed, however, the Mn stripping kinetics were very slow. After 2 min of stripping, only 1.22% Mn was stripped. It is concluded that the SSX system containing 0.5 M Versatic 10, 0.45 M LIX63 and 1.0 M TBP performed much better than the SSX system containing 0.5 M Versatic 10 and 1.0 M 4PC in terms of both manganese and calcium behaviour in extraction, scrubbing and stripping. © 2010 Elsevier B.V.

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